From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1751605AbaL2KvJ (ORCPT <rfc822;w@1wt.eu>);
	Mon, 29 Dec 2014 05:51:09 -0500
Received: from mailout2.w1.samsung.com ([210.118.77.12]:27448 "EHLO
	mailout2.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1751114AbaL2KvE (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Mon, 29 Dec 2014 05:51:04 -0500
X-AuditID: cbfec7f4-b7f126d000001e9a-1b-54a132142802
Message-id: <54A131FB.8040809@samsung.com>
Date: Mon, 29 Dec 2014 11:50:35 +0100
From: Andrzej Hajda <a.hajda@samsung.com>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101
 Thunderbird/31.3.0
MIME-version: 1.0
To: Liu Ying <Ying.Liu@freescale.com>, dri-devel@lists.freedesktop.org
Cc: devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux@arm.linux.org.uk, kernel@pengutronix.de, p.zabel@pengutronix.de,
        thierry.reding@gmail.com, shawn.guo@linaro.org, mturquette@linaro.org,
        airlied@linux.ie, andyshrk@gmail.com, stefan.wahren@i2se.com,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC v6 16/21] drm: panel: Add support for Himax HX8369A
 MIPI DSI panel
References: <1419835168-9034-1-git-send-email-Ying.Liu@freescale.com>
 <1419835168-9034-17-git-send-email-Ying.Liu@freescale.com>
 <54A11A65.1040509@samsung.com> <54A127D2.7080904@freescale.com>
In-reply-to: <54A127D2.7080904@freescale.com>
Content-type: text/plain; charset=windows-1252
Content-transfer-encoding: 7bit
X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFvrKLMWRmVeSWpSXmKPExsVy+t/xa7oiRgtDDJpeilr0njvJZHH++Bdm
	i/lHzrFaXPn6ns1i1dSdLBabHl9jtbi8aw6bxe3LvBZPJ1xks7h77wSLxdN1S5gtNq24wWbx
	c9c8FosnT0wc+DxamnvYPP4d7mfy2DnrLrvH1lumHneu7WHz2P7tAavH/e7jTB6bl9R79P81
	8Pi8SS6AK4rLJiU1J7MstUjfLoEro/nvB+aCb/sYK/5dcmxg7JrJ2MXIySEhYCKxvusdK4Qt
	JnHh3nq2LkYuDiGBpYwSG35NYIVwPjFKPD9+iaWLkYODV0BLYnZbCEgDi4CqxJIZj5lAbDYB
	TYm/m2+ygdiiAhESH1Z9BbN5BQQlfky+xwJiiwi4SZx5/4gFZCazwDYmiaazT8GKhAViJBrn
	X2WEWHaEUeLxlJ9gHZwCuhLXLn9jBFnMLKAncf+iFkiYWUBeYvOat8wTGAVmIdkxC6FqFpKq
	BYzMqxhFU0uTC4qT0nMN9YoTc4tL89L1kvNzNzFCourLDsbFx6wOMQpwMCrx8CacWBAixJpY
	VlyZe4hRgoNZSYT3DM/CECHelMTKqtSi/Pii0pzU4kOMTBycUg2M1i3+br3ZC4qsen54/Uyv
	/3vilEqahb4/u9r0J5sWnXlp+jB+gvPZhlm731h/2M9zNU5xrrtbFucUw9TDlxT/BmywZc5j
	bV1+Ufids9FF1ic3DKyWhyomnvxctUeo6eeakvnf9/+7cml/3oQlsQV+SzrfvyrODwqrfXDy
	ZxTT839JDr3insUvlFiKMxINtZiLihMBF4+mT4gCAAA=
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 12/29/2014 11:07 AM, Liu Ying wrote:
> On 12/29/2014 05:09 PM, Andrzej Hajda wrote:
>> On 12/29/2014 07:39 AM, Liu Ying wrote:
>>> This patch adds support for Himax HX8369A MIPI DSI panel.
>>>
>>> Signed-off-by: Liu Ying <Ying.Liu@freescale.com>
>>> ---
>>> v5->v6:
>>>   * Make the checkpatch.pl script be happier.
>>>   * Do not set the dsi channel number to be zero in probe(), because the MIPI DSI
>>>     bus driver would set it.
>>>
>>> v4->v5:
>>>   * Address Andrzej Hajda's comments.
>>>   * Get the bs-gpios property instead of the bs[3:0]-gpios properties.
>>>   * Implement error propagation for panel register configurations.
>>>   * Other minor changes to improve the code quality.
>>>
>>> v3->v4:
>>>   * Move the relevant dt-bindings to a separate patch to address Stefan
>>>     Wahren's comment.
>>>
>>> v2->v3:
>>>   * Sort the included header files alphabetically.
>>>
>>> v1->v2:
>>>   * Address almost all comments from Thierry Reding.
>>>   * Remove several DT properties as they can be implied by the compatible string.
>>>   * Add the HIMAX/himax prefixes to the driver's Kconfig name and driver name.
>>>   * Move the driver's Makefile entry place to sort the entries alphabetically.
>>>   * Reuse several standard DCS functions instead of inventing wheels.
>>>   * Move the panel resetting and power logics to the driver probe/remove stages.
>>>     This may simplify panel prepare/unprepare hooks. The power consumption should
>>>     not change a lot at DPMS since the panel enters sleep mode at that time.
>>>   * Add the module author.
>>>   * Other minor changes, such as coding style issues.
>>>
>>>   drivers/gpu/drm/panel/Kconfig               |   5 +
>>>   drivers/gpu/drm/panel/Makefile              |   1 +
>>>   drivers/gpu/drm/panel/panel-himax-hx8369a.c | 614 ++++++++++++++++++++++++++++
>>>   3 files changed, 620 insertions(+)
>>>   create mode 100644 drivers/gpu/drm/panel/panel-himax-hx8369a.c
>>>
>>> diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
>>> index 024e98e..81b0bf0 100644
>>> --- a/drivers/gpu/drm/panel/Kconfig
>>> +++ b/drivers/gpu/drm/panel/Kconfig
>>> @@ -16,6 +16,11 @@ config DRM_PANEL_SIMPLE
>>>   	  that it can be automatically turned off when the panel goes into a
>>>   	  low power state.
>>>
>>> +config DRM_PANEL_HIMAX_HX8369A
>>> +	tristate "Himax HX8369A panel"
>>> +	depends on OF
>>> +	select DRM_MIPI_DSI
>>> +
>>>   config DRM_PANEL_LD9040
>>>   	tristate "LD9040 RGB/SPI panel"
>>>   	depends on OF && SPI
>>> diff --git a/drivers/gpu/drm/panel/Makefile b/drivers/gpu/drm/panel/Makefile
>>> index 4b2a043..d5dbe06 100644
>>> --- a/drivers/gpu/drm/panel/Makefile
>>> +++ b/drivers/gpu/drm/panel/Makefile
>>> @@ -1,4 +1,5 @@
>>>   obj-$(CONFIG_DRM_PANEL_SIMPLE) += panel-simple.o
>>> +obj-$(CONFIG_DRM_PANEL_HIMAX_HX8369A) += panel-himax-hx8369a.o
>>>   obj-$(CONFIG_DRM_PANEL_LD9040) += panel-ld9040.o
>>>   obj-$(CONFIG_DRM_PANEL_S6E8AA0) += panel-s6e8aa0.o
>>>   obj-$(CONFIG_DRM_PANEL_SHARP_LQ101R1SX01) += panel-sharp-lq101r1sx01.o
>>> diff --git a/drivers/gpu/drm/panel/panel-himax-hx8369a.c b/drivers/gpu/drm/panel/panel-himax-hx8369a.c
>>> new file mode 100644
>>> index 0000000..eee36a7
>>> --- /dev/null
>>> +++ b/drivers/gpu/drm/panel/panel-himax-hx8369a.c
>>> @@ -0,0 +1,614 @@
>>> +/*
>>> + * Himax HX8369A panel driver.
>>> + *
>>> + * Copyright (C) 2011-2014 Freescale Semiconductor, Inc.
>>> + *
>>> + * This program is free software; you can redistribute it and/or modify
>>> + * it under the terms of the GNU General Public License version 2 as
>>> + * published by the Free Software Foundation.
>>> + *
>>> + * This driver is based on Samsung s6e8aa0 panel driver.
>>> + */
>>> +
>>> +#include <drm/drmP.h>
>>> +#include <drm/drm_mipi_dsi.h>
>>> +#include <drm/drm_panel.h>
>>> +
>>> +#include <linux/gpio/consumer.h>
>>> +#include <linux/of_device.h>
>>> +#include <linux/regulator/consumer.h>
>>> +
>>> +#include <video/mipi_display.h>
>>> +#include <video/of_videomode.h>
>>> +#include <video/videomode.h>
>>> +
>>> +#define WRDISBV		0x51
>>> +#define WRCTRLD		0x53
>>> +#define WRCABC		0x55
>>> +#define SETPOWER	0xb1
>>> +#define SETDISP		0xb2
>>> +#define SETCYC		0xb4
>>> +#define SETVCOM		0xb6
>>> +#define SETEXTC		0xb9
>>> +#define SETMIPI		0xba
>>> +#define SETPANEL	0xcc
>>> +#define SETGIP		0xd5
>>> +#define SETGAMMA	0xe0
>>> +
>>> +#define HX8369A_MIN_BRIGHTNESS	0x00
>>> +#define HX8369A_MAX_BRIGHTNESS	0xff
>>> +
>>> +enum hx8369a_mpu_interface {
>>> +	HX8369A_DBI_TYPE_A_8BIT,
>>> +	HX8369A_DBI_TYPE_A_9BIT,
>>> +	HX8369A_DBI_TYPE_A_16BIT,
>>> +	HX8369A_DBI_TYPE_A_18BIT,
>>> +	HX8369A_DBI_TYPE_B_8BIT,
>>> +	HX8369A_DBI_TYPE_B_9BIT,
>>> +	HX8369A_DBI_TYPE_B_16BIT,
>>> +	HX8369A_DBI_TYPE_B_18BIT,
>>> +	HX8369A_DSI_CMD_MODE,
>>> +	HX8369A_DBI_TYPE_B_24BIT,
>>> +	HX8369A_DSI_VIDEO_MODE,
>>> +	HX8369A_MDDI,
>>> +	HX8369A_DPI_DBI_TYPE_C_OPT1,
>>> +	HX8369A_DPI_DBI_TYPE_C_OPT2,
>>> +	HX8369A_DPI_DBI_TYPE_C_OPT3
>>> +};
>>> +
>>> +enum hx8369a_resolution {
>>> +	HX8369A_RES_480_864,
>>> +	HX8369A_RES_480_854,
>>> +	HX8369A_RES_480_800,
>>> +	HX8369A_RES_480_640,
>>> +	HX8369A_RES_360_640,
>>> +	HX8369A_RES_480_720,
>>> +};
>>> +
>>> +struct hx8369a_panel_desc {
>>> +	const struct drm_display_mode *mode;
>>> +
>>> +	/* ms */
>>> +	unsigned int power_on_delay;
>>> +	unsigned int reset_delay;
>>> +
>>> +	unsigned int dsi_lanes;
>>> +};
>>> +
>>> +struct hx8369a {
>>> +	struct device *dev;
>>> +	struct drm_panel panel;
>>> +
>>> +	const struct hx8369a_panel_desc *pd;
>>> +
>>> +	struct regulator_bulk_data supplies[5];
>>> +	struct gpio_desc *reset_gpio;
>>> +	struct gpio_desc *bs_gpio[4];
>>> +	u8 res_sel;
>>> +};
>>> +
>>> +static inline struct hx8369a *panel_to_hx8369a(struct drm_panel *panel)
>>> +{
>>> +	return container_of(panel, struct hx8369a, panel);
>>> +}
>>> +
>>> +static int hx8369a_dcs_write(struct hx8369a *ctx, const char *func,
>>> +			     const void *data, size_t len)
>>> +{
>>> +	struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
>>> +	ssize_t ret;
>>> +
>>> +	ret = mipi_dsi_dcs_write_buffer(dsi, data, len);
>>> +	if (ret < 0) {
>>> +		dev_err(ctx->dev, "%s failed: %d\n", func, ret);
>>> +		return ret;
>>> +	}
>>> +	return 0;
>> Nitpick. You can replace 4 lines above with:
>>      if (ret < 0)
>>          dev_err(ctx->dev, "%s failed: %d\n", func, ret);
>>      return ret;
> I'll do that.
>
>>> +}
>>> +
>>> +#define hx8369a_dcs_write_seq(ctx, seq...) \
>>> +({ \
>>> +	const u8 d[] = { seq }; \
>>> +	BUILD_BUG_ON_MSG(ARRAY_SIZE(d) > 64, \
>>> +			 "DCS sequence too big for stack"); \
>>> +	hx8369a_dcs_write(ctx, __func__, d, ARRAY_SIZE(d)); \
>>> +})
>>> +
>>> +#define hx8369a_dcs_write_seq_static(ctx, seq...) \
>>> +({ \
>>> +	static const u8 d[] = { seq }; \
>>> +	hx8369a_dcs_write(ctx, __func__, d, ARRAY_SIZE(d)); \
>>> +})
>>> +
>>> +static int hx8369a_dsi_set_display_related_register(struct hx8369a *ctx)
>>> +{
>>> +	u8 sec_p = (ctx->res_sel << 4) | 0x03;
>>> +
>>> +	return hx8369a_dcs_write_seq(ctx, SETDISP, 0x00, sec_p, 0x03,
>>> +			   0x03, 0x70, 0x00, 0xff, 0x00, 0x00, 0x00,
>>> +			   0x00, 0x03, 0x03, 0x00, 0x01);
>>> +}
>>> +
>>> +static int hx8369a_dsi_set_display_waveform_cycle(struct hx8369a *ctx)
>>> +{
>>> +	return hx8369a_dcs_write_seq_static(ctx, SETCYC, 0x00, 0x1d,
>>> +					0x5f, 0x0e, 0x06);
>>> +}
>>> +
>>> +static int hx8369a_dsi_set_gip(struct hx8369a *ctx)
>>> +{
>>> +	return hx8369a_dcs_write_seq_static(ctx, SETGIP, 0x00, 0x04,
>>> +				 0x03, 0x00, 0x01, 0x05, 0x1c, 0x70,
>>> +				 0x01, 0x03, 0x00, 0x00, 0x40, 0x06,
>>> +				 0x51, 0x07, 0x00, 0x00, 0x41, 0x06,
>>> +				 0x50, 0x07, 0x07, 0x0f, 0x04);
>>> +}
>>> +
>>> +static int hx8369a_dsi_set_power(struct hx8369a *ctx)
>>> +{
>>> +	return hx8369a_dcs_write_seq_static(ctx, SETPOWER, 0x01, 0x00,
>>> +				   0x34, 0x06, 0x00, 0x0f, 0x0f, 0x2a,
>>> +				   0x32, 0x3f, 0x3f, 0x07, 0x3a, 0x01,
>>> +				   0xe6, 0xe6, 0xe6, 0xe6, 0xe6);
>>> +}
>>> +
>>> +static int hx8369a_dsi_set_vcom_voltage(struct hx8369a *ctx)
>>> +{
>>> +	return hx8369a_dcs_write_seq_static(ctx, SETVCOM, 0x56, 0x56);
>>> +}
>>> +
>>> +static int hx8369a_dsi_set_panel(struct hx8369a *ctx)
>>> +{
>>> +	return hx8369a_dcs_write_seq_static(ctx, SETPANEL, 0x02);
>>> +}
>>> +
>>> +static int hx8369a_dsi_set_gamma_curve(struct hx8369a *ctx)
>>> +{
>>> +	return hx8369a_dcs_write_seq_static(ctx, SETGAMMA, 0x00, 0x1d,
>>> +				   0x22, 0x38, 0x3d, 0x3f, 0x2e, 0x4a,
>>> +				   0x06, 0x0d, 0x0f, 0x13, 0x15, 0x13,
>>> +				   0x16, 0x10, 0x19, 0x00, 0x1d, 0x22,
>>> +				   0x38, 0x3d, 0x3f, 0x2e, 0x4a, 0x06,
>>> +				   0x0d, 0x0f, 0x13, 0x15, 0x13, 0x16,
>>> +				   0x10, 0x19);
>>> +}
>>> +
>>> +static int hx8369a_dsi_set_mipi(struct hx8369a *ctx)
>>> +{
>>> +	u8 eleventh_p = ctx->pd->dsi_lanes == 2 ? 0x11 : 0x10;
>>> +
>>> +	return hx8369a_dcs_write_seq(ctx, SETMIPI, 0x00, 0xa0, 0xc6,
>>> +				 0x00, 0x0a, 0x00, 0x10, 0x30, 0x6f,
>>> +				 0x02, eleventh_p, 0x18, 0x40);
>>> +}
>>> +
>>> +static int hx8369a_dsi_set_interface_pixel_fomat(struct hx8369a *ctx)
>>> +{
>>> +	struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
>>> +	u8 format;
>>> +	int ret;
>>> +
>>> +	switch (dsi->format) {
>>> +	case MIPI_DSI_FMT_RGB888:
>>> +	case MIPI_DSI_FMT_RGB666:
>>> +		format = 0x77;
>>> +		break;
>>> +	case MIPI_DSI_FMT_RGB565:
>>> +		format = 0x55;
>>> +		break;
>>> +	case MIPI_DSI_FMT_RGB666_PACKED:
>>> +		format = 0x66;
>>> +		break;
>>> +	default:
>>> +		dev_err(ctx->dev, "unsupported DSI pixel format\n");
>>> +		return -EINVAL;
>>> +	}
>>> +
>>> +	ret = mipi_dsi_dcs_set_pixel_format(dsi, format);
>>> +	if (ret < 0)
>>> +		dev_err(ctx->dev, "%s failed: %d\n", __func__, ret);
>>> +	return ret;
>>> +}
>> This functions could be also DSI helper, it is not specific to this panel,
>> but it is just a suggestion.
> Any documentation can reflect this could be a common DSI helper,
> maybe the MIPI DSI spec?
> I wrote this function by taking the HX8369A panel data sheet as a
> reference.

MIPI DSI specification describes MIPI_DSI_FMT_* values and
MIPI DCS specification describes 'format' values (ie. 0x77, 0x55, 0x66).
For reference please look for phrase "Table 6 Interface Pixel Formats" in
MIPI DCS specification (or in google :) ).

>
>>> +
>>> +static int hx8369a_dsi_set_column_address(struct hx8369a *ctx)
>>> +{
>>> +	struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
>>> +	const struct drm_display_mode *mode = ctx->pd->mode;
>>> +	int ret;
>>> +
>>> +	ret = mipi_dsi_dcs_set_column_address(dsi, 0, mode->hdisplay - 1);
>>> +	if (ret < 0)
>>> +		dev_err(ctx->dev, "%s failed: %d\n", __func__, ret);
>>> +	return ret;
>>> +}
>>> +
>>> +static int hx8369a_dsi_set_page_address(struct hx8369a *ctx)
>>> +{
>>> +	struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
>>> +	const struct drm_display_mode *mode = ctx->pd->mode;
>>> +	int ret;
>>> +
>>> +	ret = mipi_dsi_dcs_set_page_address(dsi, 0, mode->vdisplay - 1);
>>> +	if (ret < 0)
>>> +		dev_err(ctx->dev, "%s failed: %d\n", __func__, ret);
>>> +	return ret;
>>> +}
>>> +
>>> +static int hx8369a_dsi_write_display_brightness(struct hx8369a *ctx,
>>> +						u8 brightness)
>>> +{
>>> +	return hx8369a_dcs_write_seq(ctx, WRDISBV, brightness);
>>> +}
>>> +
>>> +static int hx8369a_dsi_write_cabc(struct hx8369a *ctx)
>>> +{
>>> +	return hx8369a_dcs_write_seq_static(ctx, WRCABC, 0x01);
>>> +}
>>> +
>>> +static int hx8369a_dsi_write_control_display(struct hx8369a *ctx)
>>> +{
>>> +	return hx8369a_dcs_write_seq_static(ctx, WRCTRLD, 0x24);
>>> +}
>>> +
>>> +#define hx8369a_dsi_init_helper(ctx, ret, name) \
>>> +({ \
>>> +	ret = hx8369a_dsi_##name(ctx); \
>>> +	if (ret < 0) \
>>> +		return ret; \
>>> +})
>> Yeah, another hack to get rid of redundant code :)
>> Two ugly things here: ## and return from macro.
>>
>>> +
>>> +static int hx8369a_dsi_panel_init(struct hx8369a *ctx)
>>> +{
>>> +	int ret;
>>> +
>>> +	hx8369a_dsi_init_helper(ctx, ret, set_display_related_register);
>>> +	hx8369a_dsi_init_helper(ctx, ret, set_display_waveform_cycle);
>>> +	hx8369a_dsi_init_helper(ctx, ret, set_gip);
>>> +	hx8369a_dsi_init_helper(ctx, ret, set_power);
>>> +	hx8369a_dsi_init_helper(ctx, ret, set_vcom_voltage);
>>> +	hx8369a_dsi_init_helper(ctx, ret, set_panel);
>>> +	hx8369a_dsi_init_helper(ctx, ret, set_gamma_curve);
>>> +	hx8369a_dsi_init_helper(ctx, ret, set_mipi);
>>> +	hx8369a_dsi_init_helper(ctx, ret, set_interface_pixel_fomat);
>>> +	hx8369a_dsi_init_helper(ctx, ret, set_column_address);
>>> +	hx8369a_dsi_init_helper(ctx, ret, set_page_address);
>>> +	hx8369a_dsi_init_helper(ctx, ret, write_cabc);
>>> +	hx8369a_dsi_init_helper(ctx, ret, write_control_display);
>> Maybe it would be better to replace the hack above with something like:
>> {
>>      int (*)(struct hx8369a *ctx) funcs[] = {
>>          hx8369a_dsi_set_display_related_register,
>>          hx8369a_dsi_set_display_waveform_cycle,
>>          ...
>>       };
>>      int ret, i;
>>
>>      for (i = 0; i < ARRAY_SIZE(funcs); ++i) {
>>          ret = funcs[i](ctx);
>>          if (ret)
>>              return ret;
>>      }
> I'll change to use this.  Thanks.
>
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int hx8369a_dsi_set_extension_command(struct hx8369a *ctx)
>>> +{
>>> +	return hx8369a_dcs_write_seq_static(ctx, SETEXTC, 0xff, 0x83, 0x69);
>>> +}
>>> +
>>> +static int hx8369a_dsi_set_maximum_return_packet_size(struct hx8369a *ctx,
>>> +						      u16 size)
>>> +{
>>> +	struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
>>> +	int ret;
>>> +
>>> +	ret = mipi_dsi_set_maximum_return_packet_size(dsi, size);
>>> +	if (ret < 0)
>>> +		dev_err(ctx->dev,
>>> +			"error %d setting maximum return packet size to %d\n",
>>> +			ret, size);
>>> +	return ret;
>>> +}
>>> +
>>> +static int hx8369a_dsi_set_sequence(struct hx8369a *ctx)
>>> +{
>>> +	struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
>>> +	int ret;
>>> +
>>> +	ret = hx8369a_dsi_set_extension_command(ctx);
>>> +	if (ret < 0)
>>> +		goto out;
>>> +
>>> +	ret = hx8369a_dsi_set_maximum_return_packet_size(ctx, 4);
>>> +	if (ret < 0)
>>> +		goto out;
>>> +
>>> +	ret = hx8369a_dsi_panel_init(ctx);
>>> +	if (ret < 0)
>>> +		goto out;
>>> +
>>> +	ret = mipi_dsi_dcs_exit_sleep_mode(dsi);
>>> +	if (ret < 0) {
>>> +		dev_err(ctx->dev, "failed to exit sleep mode: %d\n", ret);
>>> +		goto out;
>>> +	}
>>> +
>>> +	ret = mipi_dsi_dcs_set_display_on(dsi);
>>> +	if (ret < 0) {
>>> +		dev_err(ctx->dev, "failed to set display on: %d\n", ret);
>>> +		goto out;
>>> +	}
>>> +
>>> +	/*
>>> +	 * It's necessary to wait 120msec after sending the Sleep Out
>>> +	 * command before Sleep In command can be sent, according to
>>> +	 * the HX8369A data sheet.
>>> +	 */
>>> +	msleep(120);
>>> +out:
>>> +	return ret;
>>> +}
>>> +
>>> +static int hx8369a_dsi_disable(struct drm_panel *panel)
>>> +{
>>> +	struct hx8369a *ctx = panel_to_hx8369a(panel);
>>> +
>>> +	return hx8369a_dsi_write_display_brightness(ctx,
>>> +						HX8369A_MIN_BRIGHTNESS);
>>> +}
>>> +
>>> +static int hx8369a_dsi_unprepare(struct drm_panel *panel)
>>> +{
>>> +	struct hx8369a *ctx = panel_to_hx8369a(panel);
>>> +	struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
>>> +	int ret;
>>> +
>>> +	ret = mipi_dsi_dcs_enter_sleep_mode(dsi);
>>> +	if (ret < 0) {
>>> +		dev_err(ctx->dev, "failed to enter sleep mode: %d\n", ret);
>>> +		goto out;
>>> +	}
>>> +
>>> +	ret = mipi_dsi_dcs_set_display_off(dsi);
>>> +	if (ret < 0) {
>>> +		dev_err(ctx->dev, "failed to set display off: %d\n", ret);
>>> +		goto out;
>>> +	}
>>> +
>>> +	/*
>>> +	 * This is to allow time for the supply voltages and clock
>>> +	 * circuits to stablize, according to the HX8369A data sheet.
>>> +	 */
>>> +	msleep(5);
>>> +out:
>>> +	return ret;
>>> +}
>>> +
>>> +static int hx8369a_dsi_prepare(struct drm_panel *panel)
>>> +{
>>> +	struct hx8369a *ctx = panel_to_hx8369a(panel);
>>> +
>>> +	return hx8369a_dsi_set_sequence(ctx);
>>> +}
>>> +
>>> +static int hx8369a_dsi_enable(struct drm_panel *panel)
>>> +{
>>> +	struct hx8369a *ctx = panel_to_hx8369a(panel);
>>> +
>>> +	return hx8369a_dsi_write_display_brightness(ctx,
>>> +						HX8369A_MAX_BRIGHTNESS);
>>> +}
>>> +
>>> +static int hx8369a_get_modes(struct drm_panel *panel)
>>> +{
>>> +	struct drm_connector *connector = panel->connector;
>>> +	struct drm_device *drm = panel->drm;
>>> +	struct hx8369a *ctx = panel_to_hx8369a(panel);
>>> +	struct drm_display_mode *mode;
>>> +	const struct drm_display_mode *m = ctx->pd->mode;
>>> +
>>> +	mode = drm_mode_duplicate(drm, m);
>>> +	if (!mode) {
>>> +		dev_err(drm->dev, "failed to add mode %ux%u@%u\n",
>>> +			m->hdisplay, m->vdisplay, m->vrefresh);
>>> +		return 0;
>>> +	}
>>> +
>>> +	drm_mode_set_name(mode);
>>> +	mode->type = DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED;
>>> +
>>> +	connector->display_info.bpc = 8;
>>> +	connector->display_info.width_mm = mode->width_mm;
>>> +	connector->display_info.height_mm = mode->height_mm;
>>> +
>>> +	drm_mode_probed_add(connector, mode);
>>> +
>>> +	return 1;
>>> +}
>>> +
>>> +static const struct drm_panel_funcs hx8369a_dsi_drm_funcs = {
>>> +	.disable = hx8369a_dsi_disable,
>>> +	.unprepare = hx8369a_dsi_unprepare,
>>> +	.prepare = hx8369a_dsi_prepare,
>>> +	.enable = hx8369a_dsi_enable,
>>> +	.get_modes = hx8369a_get_modes,
>>> +};
>>> +
>>> +static int hx8369a_power_on(struct hx8369a *ctx)
>>> +{
>>> +	int ret;
>>> +
>>> +	ret = regulator_bulk_enable(ARRAY_SIZE(ctx->supplies), ctx->supplies);
>>> +	if (ret < 0)
>>> +		return ret;
>>> +
>>> +	msleep(ctx->pd->power_on_delay);
>>> +
>>> +	gpiod_set_value(ctx->reset_gpio, 1);
>>> +	usleep_range(50, 60);
>>> +	gpiod_set_value(ctx->reset_gpio, 0);
>>> +
>>> +	msleep(ctx->pd->reset_delay);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int hx8369a_power_off(struct hx8369a *ctx)
>>> +{
>>> +	return regulator_bulk_disable(ARRAY_SIZE(ctx->supplies),
>>> +				      ctx->supplies);
>>> +}
>>> +
>>> +static void hx8369a_vm_to_res_sel(struct hx8369a *ctx)
>>> +{
>>> +	const struct drm_display_mode *mode = ctx->pd->mode;
>>> +
>>> +	switch (mode->hdisplay) {
>>> +	case 480:
>>> +		switch (mode->vdisplay) {
>>> +		case 864:
>>> +			ctx->res_sel = HX8369A_RES_480_864;
>>> +			break;
>>> +		case 854:
>>> +			ctx->res_sel = HX8369A_RES_480_854;
>>> +			break;
>>> +		case 800:
>>> +			ctx->res_sel = HX8369A_RES_480_800;
>>> +			break;
>>> +		case 640:
>>> +			ctx->res_sel = HX8369A_RES_480_640;
>>> +			break;
>>> +		case 720:
>>> +			ctx->res_sel = HX8369A_RES_480_720;
>>> +			break;
>>> +		default:
>>> +			break;
>>> +		}
>>> +		break;
>>> +	case 360:
>>> +		if (mode->vdisplay == 640)
>>> +			ctx->res_sel = HX8369A_RES_360_640;
>>> +		break;
>>> +	default:
>>> +		break;
>>> +	}
>>> +}
>>> +
>>> +static const struct drm_display_mode truly_tft480800_16_e_mode = {
>>> +	.clock = 26400,
>>> +	.hdisplay = 480,
>>> +	.hsync_start = 480 + 8,
>>> +	.hsync_end = 480 + 8 + 8,
>>> +	.htotal = 480 + 8 + 8 + 8,
>>> +	.vdisplay = 800,
>>> +	.vsync_start = 800 + 6,
>>> +	.vsync_end = 800 + 6 + 6,
>>> +	.vtotal = 800 + 6 + 6 + 6,
>>> +	.vrefresh = 60,
>>> +	.width_mm = 45,
>>> +	.height_mm = 76,
>>> +};
>>> +
>>> +static const struct hx8369a_panel_desc truly_tft480800_16_e_dsi = {
>>> +	.mode = &truly_tft480800_16_e_mode,
>>> +	.power_on_delay = 10,
>>> +	.reset_delay = 10,
>>> +	.dsi_lanes = 2,
>>> +};
>>> +
>>> +static const struct of_device_id hx8369a_dsi_of_match[] = {
>>> +	{
>>> +		.compatible = "truly,tft480800-16-e-dsi",
>>> +		.data = &truly_tft480800_16_e_dsi,
>>> +	}, {
>>> +		/* sentinel */
>>> +	},
>>> +};
>>> +MODULE_DEVICE_TABLE(of, hx8369a_dsi_of_match);
>>> +
>>> +static int hx8369a_dsi_probe(struct mipi_dsi_device *dsi)
>>> +{
>>> +	struct device *dev = &dsi->dev;
>>> +	const struct of_device_id *of_id =
>>> +			of_match_device(hx8369a_dsi_of_match, dev);
>>> +	struct hx8369a *ctx;
>>> +	int ret, i;
>>> +
>>> +	ctx = devm_kzalloc(dev, sizeof(*ctx), GFP_KERNEL);
>>> +	if (!ctx)
>>> +		return -ENOMEM;
>>> +
>>> +	ctx->dev = dev;
>>> +
>>> +	if (of_id) {
>>> +		ctx->pd = of_id->data;
>>> +	} else {
>>> +		dev_err(dev, "cannot find compatible device\n");
>>> +		return -ENODEV;
>>> +	}
>>> +
>>> +	hx8369a_vm_to_res_sel(ctx);
>>> +
>>> +	ctx->supplies[0].supply = "vdd1";
>>> +	ctx->supplies[1].supply = "vdd2";
>>> +	ctx->supplies[2].supply = "vdd3";
>>> +	ctx->supplies[3].supply = "dsi-vcc";
>>> +	ctx->supplies[4].supply = "vpp";
>>> +	ret = devm_regulator_bulk_get(dev, ARRAY_SIZE(ctx->supplies),
>>> +				      ctx->supplies);
>>> +	if (ret < 0) {
>>> +		dev_info(dev, "failed to get regulators: %d\n", ret);
>>> +		return ret;
>>> +	}
>>> +
>>> +	ctx->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
>>> +	if (IS_ERR(ctx->reset_gpio)) {
>>> +		dev_info(dev, "cannot get reset-gpios %ld\n",
>>> +			 PTR_ERR(ctx->reset_gpio));
>>> +		return PTR_ERR(ctx->reset_gpio);
>>> +	}
>>> +
>>> +	for (i = 0; i < 4; i++) {
>>> +		ctx->bs_gpio[i] = devm_gpiod_get_index(dev, "bs", i,
>>> +							GPIOD_OUT_HIGH);
>>> +		if (!IS_ERR_OR_NULL(ctx->bs_gpio[i]))
>>> +			dev_dbg(dev, "bs%d-gpio is configured\n", i);
>> Are you sure you want to continue probe on error during getting gpios?
> There could be holes in the gpio list as mentioned in [1].
> For this panel, the potential holes mean that the relevant
> gpios are not controlled by the driver but only by the
> hardware.
>
> Perhaps, I need to handle the error case.
> I tried to implement it in the following way.
>
> ctx->bs_gpio[i] = devm_gpiod_get_index(dev, "bs", i,
>                                         GPIOD_OUT_HIGH);
> if (!IS_ERR_OR_NULL(ctx->bs_gpio[i])) {
>      dev_dbg(dev, "bs%d-gpio is configured\n", i);
> } else if (IS_ERR(ctx->bs_gpio[i])) {
>      dev_info(dev, "failed to get bs%d-gpio\n", i);
>      return PTR_ERR(ctx->bs_gpio[i]);
> }
>
> But, I get this in dmesg.  Any idea?
> [    1.625634] panel-hx8369a-dsi 21e0000.mipi.0: failed to get bs0-gpio
> [    1.633060] panel-hx8369a-dsi: probe of 21e0000.mipi.0 failed with 
> error -2

I guess you should use devm_gpiod_get_index_optional .

Regards
Andrzej

>
> [1] Documentation/devicetree/bindings/gpio/gpio.txt.
>
> Regards,
>
> Liu Ying
>
>> After addressing above comments you can add:
>>
>> Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
>>
>>
>>
>> Regards
>> Andrzej
>>
>>
>>> +	}
>>> +
>>> +	ret = hx8369a_power_on(ctx);
>>> +	if (ret < 0) {
>>> +		dev_err(dev, "cannot power on\n");
>>> +		return ret;
>>> +	}
>>> +
>>> +	drm_panel_init(&ctx->panel);
>>> +	ctx->panel.dev = dev;
>>> +	ctx->panel.funcs = &hx8369a_dsi_drm_funcs;
>>> +
>>> +	ret = drm_panel_add(&ctx->panel);
>>> +	if (ret < 0)
>>> +		return ret;
>>> +
>>> +	mipi_dsi_set_drvdata(dsi, ctx);
>>> +
>>> +	dsi->lanes = ctx->pd->dsi_lanes;
>>> +	dsi->format = MIPI_DSI_FMT_RGB888;
>>> +	dsi->mode_flags = MIPI_DSI_MODE_VIDEO |
>>> +			  MIPI_DSI_MODE_VIDEO_BURST |
>>> +			  MIPI_DSI_MODE_VIDEO_SYNC_PULSE;
>>> +	ret = mipi_dsi_attach(dsi);
>>> +	if (ret < 0)
>>> +		drm_panel_remove(&ctx->panel);
>>> +
>>> +	return ret;
>>> +}
>>> +
>>> +static int hx8369a_dsi_remove(struct mipi_dsi_device *dsi)
>>> +{
>>> +	struct hx8369a *ctx = mipi_dsi_get_drvdata(dsi);
>>> +
>>> +	mipi_dsi_detach(dsi);
>>> +	drm_panel_remove(&ctx->panel);
>>> +	return hx8369a_power_off(ctx);
>>> +}
>>> +
>>> +static struct mipi_dsi_driver hx8369a_dsi_driver = {
>>> +	.probe = hx8369a_dsi_probe,
>>> +	.remove = hx8369a_dsi_remove,
>>> +	.driver = {
>>> +		.name = "panel-hx8369a-dsi",
>>> +		.of_match_table = hx8369a_dsi_of_match,
>>> +	},
>>> +};
>>> +module_mipi_dsi_driver(hx8369a_dsi_driver);
>>> +
>>> +MODULE_DESCRIPTION("Himax HX8369A panel driver");
>>> +MODULE_AUTHOR("Liu Ying <Ying.Liu@freescale.com>");
>>> +MODULE_LICENSE("GPL v2");